Catalytic dimerization of olefins with cobalt complexes

ABSTRACT

A catalytic process for the dimerization of olefins utilizing a cobalt(II) complex activated by the presence of an alkylaluminum halide. Propylene is dimerized with a catalyst prepared by mixing bis(quinoline)dibromocobalt(II) and ethylaluminum dichloride in chlorobenzene.

United States Patent [151 3,686,353 Dunn 1 Aug. 22, 1972 [54] CATALYTICDIMERIZATION OF 3,511,891 5/1970 Taylor et a1. ..260/683. 1 5

OLEFINS WITH COBALT COMPLE FOREIGN PATENTS OR APPLICATIONS [72]Inventor: Howard E. Dunn, Evansville, Ind.

62,561 7/ 1968 Germany ..260/683. 15 [73] Assignee: Phillips PetroleumCompany 22 Filed; J ne 1 1970 Primary Examiner-Paul Coughlan, Jr. 1 ppNo 47 633 Att0rney-Y0ung and Qulgg [57] ABSTRACT 5 683'l5 252/431 Acatalytic process for the dimerization of olefins I. U I I e u e lihl al e n s a a a u a I e a u n n u l a n I u a I D a [58] Field of Searcpresence of an alkylaluminum halide. Propylene is 56] References Citeddlmenzed wlth a catalyst prepared by mixing b|s(qumoline )dibromocobalt(II dichloride in chlorobenzene.

and ethylaluminum 7 Claims, No Drawings CATALYTIC DLMERIZATION F OLEFINSWITH COBALT COMPLEXES This invention relates to the catalyticdimerization of monoolefins by the use of a cobalt (H) complex inthepresence of an alkylaluminum halide activator. This invention in anotheraspect relates to the catalytic dimerization of propylene by the use ofactivated cobalt(II) complexes.

Dimerization of lower aliphatic monoolefins, for example, propylene, isof interest to the art. Of particular importance is the conversion .ofpropylene into linear hexenes. These linear hexenes can be convertedinto oxo-alcohols to be used as plasticizers, or dimerized to dodecaneswhich would be useful as detergent intermediates.

Cationic dimerization systems for propylene have been found to give2-methylpentenes and 3-methylpentenes as the major products. Thesereactions are usually accompanied by a considerable amount of polymerformation. Anionic dimerization of propylene gives 4-methylpentene-l asthe major product. These reactions are usually carried out inhydrocarbon dispersions of alkali metals and require relatively hightemperature. Also, long induction period requirements are common inanionic dimerizations. Most common methods of olefin dimerizationrequire rather severe reaction conditions favoring the production ofbranched products.

It is an object of this invention to provide an olefin dimerizationprocess that is operative under mild conditions.

I have found that olefms, for example, propylene can be dimerized over acatalyst comprising L CoX wherein L represents ligand, Co-representscobalt, and X represents halogen; when the aforementioned complex hasbeen activated by the presence of an alkylaluminum halide. Thisdimerization process can be carried out under very mild conditions. Thevarious activated cobalt(ll) complexes used in the dimerization processof my invention produced isomer distributions with very littlevariation.

The olefms to which the present dimerization process is directed includecyclic monoolefins having up to about 12 carbon atoms per molecule andacyclic monoolefins having from about two to 12 carbon atoms, inclusive,where the acyclic monoolefin can be a terminal or internal olefin,branched or unbranched. Examples of suitable monoolefms which can beused according to the present invention are ethylene, propylene,butene-l, butene-2, pentene-l, pentene-2, cyclopentene, cyclohexene,3,4,5-trimethylcyclohexene, 3-methylbutene-l, cycloheptene, hexene-2,heptene-l, cyclooctene, 4,4-dimethylheptene-2, decene-l, dodecene-l andthe like and mixtures thereof.

Activated cobalt complexes containing a variety of ligands, for example,amines and phosphines can be used as dimerization catalysts for theaforementioned olefins.

Examination of the results of my process indicated that even though theligand was varied the distribution of the isometric product stayedrelatively constant. The cobalt catalyst complexes used in the method ofmy invention were carried in suitable halogenated hydrocarbon solvents,for example chlorobenzene, and were activated with methylaluminumsesquichloride or ethylaluminum dichloride. The rates of dimerization ofpropylene over cobalt catalyst complexes activated by the twoaforementioned activators were essentially equal and the variance ofactivator had very little effect on the isomer distribution of theproducts. Other alkylaluminum halides which can be used arediethylaluminum chloride, dihexylaluminum bromide, dimethylaluminumchloride, methylaluminum chloride and the like. The process of myinvention requires an aluminum to cobalt gram atom rau'o of at least 6:1in order to activate the cobalt catalyst. Gram atom ratios below 6:1yielded a dead or only slightly active catalyst and with ratios aboveabout 9:1, having little effect on the dimerization rate.

The temperature of my invention may vary broadly from 25 to C. Themonoolefin pressure can range from 1 to psig or to the liquificationpressure at operating temperature. The concentration of the cobalt(H)complex in the solvent is not critical and can range from one-millionthmolar to the saturation point, preferably being about 0.1 to 0.00001molar.

Soluble cobalt(H) complexes were used in the process of my invention todimerize olefins, for example propylene. These soluble, cobalt complexeswere selected from bis(pyridine, phosphine, or quinoline)dihalocobalt(H)compounds. The aforementioned cobalt(H) complexes were activated by thepresence of alkylaluminum halides, therefor carried in halogenatedhydrocarbon solvents.

The following six examples are intended for illustrative purposes andare not intended to limit the scope of the process of my invention.

EXAMPLE I Propylene (30 psig) was pressured into a 7 oz. glass reactorcontaining bis(4-ethylpyridine)dibromocobalt(ll) (0.0433 g., 0.1 mmol),chlorobenzene (20 ml) and 1 ml (1 mmol) of a 1 M ethylaluminumdichloride solution in chlorobenzene. The reaction was carried out for18.5 hours at about 10 to 25 C. with the propylene pressure maintainedat 30 psig. Deionized water (10 ml) was added, the organic layer wasdecanted, and distilled at atmospheric pressure: bp 5060 C., 4.50 g.

A 1.25 g. sample of the above distillate was placed over 0.0195 g. ofplatinum oxide and hydrogen was supplied at 30 psig for 4.75 hours toinsure complete reduction. Analysis (glpc) of the resulting hexanesindicated the composition of the hexene product mixture was:2-methylpentenes, 67.3 percent; n-hexenes, 30.7 percent;2,3-dimethylbutenes, 1.4 percent; and 3- methylpentenes, 0.6 percent.

EXAMPLE II Propylene (30 psig) was pressured into a 7 oz. glass reactorcontaining bis(quinoline)dibromocobalt(ll) (0.1173 g., 0.1 mmol),chlorobenzene (20 ml), and 1 ml of a 1 M ethylaluminum dichloridesolution in chlorobenzene. ('Ihe propylene was pressured into thereactor after the other above-named components had been stirred at roomtemperature for 2 minutes.) The reaction was carried out at 23.224.2 C.for 6 hours at 30 psig propylene. Deionized water (2 ml) was added, theorganic layer was decanted and was distilled at atmospheric pressure: bp60-67 C.; hexene fraction, 4.52 g.

Reduction over platinum oxide was carried out as above. Analysis (glpc)of the resulting hexanes indicated the composition of the hexene productmixture was: 2-methylpentenes, 70.8 percent; n-hexenes, 25.3 percent;and 2,3-dimethylbutenes, 5.7 percent.

EXAIVIPLE [H The above procedure employed withbis(quinoline)dibromocobalt(H) was also employed withbis(isoquinoline)dibromocobalt(H). The temperature ranged between23.224.2 C. over a 6-hour reaction period. Deionized water (2 ml) wasadded, the organic layer decanted, and distilled at atmosphericpressure: bp 6067 C.; hexene fraction, 8.44 g.

A 2 ml quantity of the above hexene fraction was reduced as describedabove over a 6-hour period. Analysis (glpc) of the resulting hexanesindicated the composition of the hexene product mixture was: 2-methy1-pentenes, 70.4 percent; n-hexenes, 25.6 percent; 2,3- dimethylbutenes,4.0 percent.

EXAMPLE IV Blue bis(pyridine)dichlorocobalt(II) (0.0288 g., 0.1 mmol)was charged to a 7 oz. glass reactor. The reactor was capped and flushedwith nitrogen. Chlorobenzene (20 ml) was added immediately. The contentsof the reactor were placed under propylene psig) and 1.5 ml of a l Methylaluminum dichloride solution in chlorobenzene was added. Themixture became light blue. Propylene pressure was then increased to 30psig and maintained there for 2.5 hours at 5.87.8 C. At the end of thereaction period the propylene pressure was reduced to 5 psig anddeionized water (10 ml) was added. The organic layer was decanted anddistilled at atmospheric pressure: bp 30100 C.; therefore hexenefraction, 33.16 g.

A 2 ml fraction of the above distillate was reduced as above over a5-hour period. Analysis (glpc) of the resulting hexanes indicated thecomposition of the hexene product mixture was: 2-methylpentenes, 73.1percent; n-hexenes, 24.8 percent; 2,3-dimethylbutenes, 2.0 percent.

EXAMPLE V The procedure applied under Example IV above was employed withthe mauve form of bis(pyridine)dichlorocobalt(ll). The solution wasinitially mauve but turned blue after approximately 5 minutes. Afterdestroying the catalyst with deionized water, the organic layer wasdecanted and distilled at atmospheric pressure: bp 53100 C.; hexenefraction, 17.24 g.

A 2 ml portion of the hexene fraction was reduced as EXAMPLE VIPropylene (40 psig) was pressured into a 7 oz. glass reactor containingbis(triphenylphosphine)dibromocobalt(ll) (0.0743 g, 0.1 mmol)chlorobenzene (20 ml) and 1 ml (1.0 mmol) ofa l M ethylaluminumdichloride solution in chlorobenzene. The reaction was owed to proceedfor 6.5 hours at 40 psig propylene. Upon distillation (bp 66-67.5 C.) a7.8 g. hexene fraction was collected. Analysis (glpc) of the resultinghexanes following reduction indicated the composition of the hexeneproduct mixture was: 2- methylpentenes, 65.1 percent; n-hexenes, 27.2percent; 2,3-dimethylbutenes, 6.9 percent; 3-methylpentenes, 0.8percent.

As will be evident to those skilled in the art, many variations andmodifications can be practiced in view of the foregoing disclosure. Suchvariations and modifications are believed to be within the spirit andscope of the invention.

What I claim is:

l. A catalytic process for the dimerization of olefins, comprising;contacting olefins having from two to 12 carbon atoms per molecule witha bis(quinoline)diha.locobalt(ll) complex which has been activated bythe presence of an alkylaluminum halide with the aluminum to cobalt gramatom ratio being at least 6:1, wherein both the cobalt(II) complex andthe alkylaluminum halide are carried by a halogenated hydrocarbonsolvent.

2. A process according to claim 1 wherein the cobalt(II) complex is bis(quinoline )dibromocobalt(ll).

3. A process according to claim 1 wherein the alkylaluminum halide isethylaluminum dichloride.

4. A process according to claim 1 wherein the alkylaluminum halide ismethylaluminum sesquichlon'de.

5. A process according to claim 1 wherein the halogenated hydrocarbonsolvent is chlorobenzene.

6. A catalytic process for the dimerization of olefins, comprising;contacting olefins having from two to 12 carbon atoms per molecule witha bis(quinoline)dibromocobalt(ll) complex which has been activated bythe presence of ethylaluminum dichloride with the aluminum to cobaltgram atom ratio being at least 6:1, wherein both the cobalt(H) complexand the

2. A process according to claim 1 wherein the cobalt(II) complex isbis(quinoliNe)dibromocobalt(II).
 3. A process according to claim 1wherein the alkylaluminum halide is ethylaluminum dichloride.
 4. Aprocess according to claim 1 wherein the alkylaluminum halide ismethylaluminum sesquichloride.
 5. A process according to claim 1 whereinthe halogenated hydrocarbon solvent is chlorobenzene.
 6. A catalyticprocess for the dimerization of olefins, comprising; contacting olefinshaving from two to 12 carbon atoms per molecule with abis(quinoline)dibromocobalt(II) complex which has been activated by thepresence of ethylaluminum dichloride with the aluminum to cobalt gramatom ratio being at least 6:1, wherein both the cobalt(II) complex andthe ethylaluminum dichloride are carried by a halogenated hydrocarbonsolvent.
 7. A process according to claim 6 wherein the halogenatedhydrocarbon solvent is chlorobenzene.